Linear alkylbenzenes are widely used as intermediates to make detergent compounds. Particularly, straight chain alkylbenzene sulfonates are important surfactants in commercial detergent products because of their detergent properties, ease of biodegradation and other desirable properties.
The advantages of the alkylbenzene sulfonates are known to vary somewhat in view of the isomer mix of the alkylbenzene intermediate.
Linear alkylbenzene sulfonate (LAS) is produced in great volumes using linear alkylbenzene intermediates manufactured by two major commercial processes which differ primarily in the catalyst system employed. One process uses an aluminum chloride catalyst and the other process uses hydrogen fluoride catalyst. The phenyl isomer distribution in LAS produced from intermediates of the two processes are recognized as "high" 2-phenyl product from the AlCl.sub.3 process and as "low" 2-phenyl product from the HF process. Typical phenyl isomer distribution for average molecular weight products characterized as high 2-phenyl is about 30% 2-phenyl isomer and about 22% 3-phenyl isomer whereas the products characterized as low 2-phenyl is about 20% 2-phenyl isomer and about 20% 3-phenyl isomer or having a more balanced isomer distribution.
It is known that the sulfonates of long chain alkylbenzenes have different properties depending upon the position of the aromatic group on the alkyl chain. For most applications in the surface active field, arylalkanes are desired in which the amount of the 2-arylalkane isomer is relatively low and various processes have been reported for obtaining arylalkane products containing minimum amounts of 2-arylalkane isomers. However, for certain applications, for example when one is more interested in obtaining maximum solubility in aqueous detergent formulations, a product containing a relatively high percentage of compounds in which the aromatic substituent is in the 2 or 3 position and correspondingly smaller percentages of isomers in which the aromatic substituent is positioned centrally with respect to the alkyl chain are advantageous. See for example U.S. Pat. No. 3,585,253 and U.S. Pat. No. 3,776,962.
Although processes are available to produce high 2-phenyl products having adequate aqueous solubility such processes represent a significant cost and a loss of other desirable properties of the low 2-phenyl product. Accordingly, to meet the substantial market demand for alkylbenzene sulfonates having good aqueous solubility in aqueous detergent formulations the detergent formulator has employed certain hydrotopes e.g. sodium xylene sulfonate in conjunction with the low 2-phenyl product to improve its aqueous solubility (see for example, U.S. Pat. No. 3,231,504). The use of such hydrotropes suffers the disadvantages of adding to the cost of the formulation without any improvement in its detergent properties. These and other disadvantages are overcome by the present invention.